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The primary objectives of this study are to compare the efficacy, safety, and tolerability of tenofovir disoproxil fumarate (TDF) versus adefovir dipivoxil (ADV) for the treatment of HBeAg-positive chronic hepatitis B. Participants will receive TDF or ADV for 48 weeks (double-blind). After 48 weeks, eligible participants switched to open-label TDF for up to 480 weeks.

Complete response was a composite endpoint defined as histological response and HBV DNA < 400 copies/mL. Histological response was based on the Knodell numerical scoring of liver biopsy specimens and defined as at least a 2-point reduction in Knodell necroinflammatory score without worsening in Knodell fibrosis score. The Knodell necroinflammatory score is the combined necrosis and inflammation domain scores and ranges from 0 to 14; the Knodell fibrosis domain score ranges from 0 to 4.

A participant was a nonresponder for the primary endpoint if either biopsy (baseline or end-of-treatment) was missing or if there was not an HBV DNA value available at or beyond Week 40.

Histological response was based on the Knodell numerical scoring of liver biopsy specimens and defined as at least a 2-point reduction in Knodell necroinflammatory score without worsening in Knodell fibrosis score. The Knodell necroinflammatory score is the combined necrosis and inflammation domain scores and ranges from 0 to 14; the Knodell fibrosis domain score ranges from 0 to 4.

Histological response was based on the Knodell numerical scoring of liver biopsy specimens and defined as at least a 2-point reduction in Knodell necroinflammatory score without worsening in Knodell fibrosis score. The Knodell necroinflammatory score is the combined necrosis and inflammation domain scores and ranges from 0 to 14; the Knodell fibrosis domain score ranges from 0 to 4.

The Knodell necroinflammatory score is the combined score for necrosis and inflammation domains of the Knodell scoring system, and ranges from 0 (best) to 14 (worst). The Ishak score measures the degree of liver fibrosis (scarring) caused by chronic necroinflammation (inflammation leading to cell death) and ranges from 0 (best) to 6 (worst).

The Knodell necroinflammatory score is the combined score for necrosis and inflammation domains of the Knodell scoring system, and ranges from 0 (best) to 14 (worst). The Ishak score measures the degree of liver fibrosis (scarring) caused by chronic necroinflammation (inflammation leading to cell death) and ranges from 0 (best) to 6 (worst).

Participants were ranked as having improvement, no change, worsening, or missing data (compared to Baseline) based on the Knodell scoring system, and results are presented as the percentage of participants in each category. The Knodell necroinflammatory score is the combined score for necrosis and inflammation domains of the Knodell scoring system, which ranges from 0 (best) to 14 (worst). The Knodell fibrosis domain score ranges from 0 (best) to 4 (worst). A decrease of 1 point or more indicated improvement, and an increase of 1 point or more indicated worsening.

Participants were ranked as having improvement, no change, worsening, or missing data (compared to Baseline) based on the Knodell scoring system, and results are presented as the percentage of participants in each category. The Knodell necroinflammatory score is the combined score for necrosis and inflammation domains of the Knodell scoring system, which ranges from 0 (best) to 14 (worst). The Knodell fibrosis domain score ranges from 0 (best) to 4 (worst). A decrease of 1 point or more indicated improvement, and an increase of 1 point or more indicated worsening.

ALT normalization was defined as ALT > upper limit of normal (ULN) at baseline and within the normal range at the end of blinded treatment. The ULN was 43 U/L for males and 34 U/L for females aged 18 to < 69, and 35 U/L for males and 32 U/L for females aged ≥ 69.

ALT normalization was defined as ALT > ULN at baseline and within the normal range at Week 96. The ULN was 43 U/L for males and 34 U/L for females aged 18 to < 69, and 35 U/L for males and 32 U/L for females aged ≥ 69.

ALT normalization was defined as ALT > ULN at baseline and within the normal range at the subsequent time point. The ULN was 43 U/L for males and 34 U/L for females aged 18 to < 69, and 35 U/L for males and 32 U/L for females aged ≥ 69.

Percentage of Participants With ALT Normalization at Weeks 432 and 480 [ Time Frame: Baseline; Weeks 432 and 480 ]

ALT normalization was defined as ALT > ULN at baseline and within the normal range at the subsequent time point. The ULN was 43 U/L for males and 34 U/L for females aged 18 to < 69, and 35 U/L for males and 32 U/L for females aged ≥ 69.

HBeAg loss was defined as HBeAg positive at baseline and HBeAg negative at Week 48. Seroconversion to anti-HBe was defined as change of detectable antibody to HBeAg from negative at baseline to positive at Week 48.

Percentage of Participants With HBeAg Loss or Seroconversion to Anti-HBe at Week 96 [ Time Frame: Baseline; Week 96 ]

HBeAg loss was defined as HBeAg positive at baseline and HBeAg negative at Week 96. Seroconversion to anti-HBe was defined as change of detectable antibody to HBeAg from negative at baseline to positive at Week 96.

HBsAg loss was defined as HBsAg positive at baseline and HBsAg negative at Week 48. Seroconversion to anti-HBs was defined as change of detectable antibody to HBsAg from negative at baseline to positive at Week 48.

Percentage of Participants With HBsAg Loss or Seroconversion to Anti-HBs at Week 96 [ Time Frame: Baseline; Week 96 ]

HBsAg loss was defined as HBsAg positive at baseline and HBsAg negative at the subsequent time point. Seroconversion to anti-HBs was defined as change of detectable antibody to HBsAg from negative at baseline to positive at the subsequent time point.

HBsAg loss was defined as HBsAg positive at baseline and HBsAg negative at the subsequent time point. Seroconversion to anti-HBs was defined as change of detectable antibody to HBsAg from negative at baseline to positive at the subsequent time point.

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL, those with viral breakthrough, and those who discontinued after Week 24 with HBV DNA ≥ 400 copies/mL.

Number of Participants With HBV Genotypic Changes From Baseline at Week 96 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 49 to 96 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 96 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 48 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 144 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 97 to 144 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 144 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 96 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 96 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 192 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 145 to 192 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 192 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 144 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 144 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 240 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 193 to 240 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 240 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 192 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 192 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 288 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 241 to 288 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 288 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 240 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 240 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 336 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 289 to 336 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 336 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 288 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 288 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 384 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 337 to 384 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 384 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 336 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 336 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 432 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 385 to 432 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 432 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 384 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 384 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

Number of Participants With HBV Genotypic Changes From Baseline at Week 480 (Resistance Surveillance) [ Time Frame: Baseline; Weeks 433 to 480 ]

Of the total number analyzed, participants evaluated for resistance included those with HBV DNA ≥ 400 copies/mL at Week 480 on TDF monotherapy, those with viral breakthrough, those who discontinued after Week 432 with HBV DNA ≥ 400 copies/mL, and those who added emtricitabine to the open-label TDF regimen after Week 432 and had HBV DNA ≥ 400 copies/mL at the time of the addition.

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Ages Eligible for Study:

18 Years to 69 Years (Adult, Older Adult)

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

No

Criteria

Key Inclusion Criteria:

A patient must meet all of the following inclusion criteria to be eligible for participation in this study:

Liver biopsy performed within 6 months of baseline and has readable biopsy slides or agrees to have a biopsy performed prior to baseline

Key Exclusion Criteria:

A patient who meets any of the following exclusion criteria is not to be enrolled in this study:

Pregnant women, women who are breast feeding or who believe they may wish to become pregnant during the course of the study

Males and females of reproductive potential who are unwilling to use an effective method of contraception during the study; for males, condoms should be used and for females, a barrier contraception method should be used